Recently, the 3rd Generation Partnership Project (3GPP) has adopted a set of standards for cellular network known as LTE or 3GPP release 8 which uses transmitter and receiver, each having multiple antennas for transmission and reception of data. As a multiple input, multiple output (MIMO) technology, LTE is designed to coordinate multiple simultaneous radio signals, and is expected to support a bit rate of greater than 100 megabits per second (Mbps). Furthermore, the Institute of Electrical and Electronics Engineers (IEEE) has adopted an 802.16m standard, which supports the International Telecommunication Union (ITU) IMT-ADVANCE (also known as “4G”) and an 802.11n standards for wireless local area network. Both standards also use MIMO technology for throughput and/or performance enhancement. Further work in MIMO technology in the form of LTE-advanced is also initiated in 3GPP.
MIMO techniques may be in the form of single-user MIMO, or SU-MIMO, which involves communications between a single base station (BS) or an access point (AP), and a single mobile station (MS), user premise equipment (UE), or subscriber station (SS). During the uplink, a MS may transmit multiple independent signal streams to the BS using the same transmission channel. In the downlink, the BS may transmit multiple independent signal streams to the MS. Multiple-user MIMO, or MU-MIMO, is concerned with communication between the BS and multiple MSs or SSs. During the uplink, multiple MSs transmit data to the BS in the same transmission channel; during the downlink, the BS transmits signals to multiple MSs in the same transmission channel. MIMO technology takes advantage of spatial multiplexing, that is signals sharing the same transmission channel but uses different signal propagation paths, or time multiplexing, that is signals sharing the same transmission channel at different time, or a combination of spatial and time multiplexing, to achieve higher throughput or performance enhancement. The recovery of the multiplexed signal streams in the receiver requires special MIMO detector to de-multiplex the composite signals stream into its independent constituents and hence recovering the original transmitted signal streams.